Refastenable mechanical fastening systems can be used in a wide number of applications. For example, such refastenable fastening systems can be used to connect one portion of a disposable absorbent article to another portion of the disposable absorbent article.
In general, mechanical fastening systems comprise a receiving/female component and an engaging/male component. In some mechanical fastening systems, the engaging member comprises a plurality of hook elements, and the receiving component comprises a plurality of loop elements. In a fastened state, the hook elements typically are entangled with the loop elements such that a connection between the engaging and receiving components is formed.
Nonwoven webs are known in the art as potential materials for use as the female component. Typically, a nonwoven female component comprises a plurality of polymeric fibers. Portions of these fibers can be joined together by fiber-to-fiber bonds to form a web having sufficient available unbonded fibers or unbonded portions of bonded fibers and web integrity. The fiber-to-fiber bonds are typically formed by fusing portions fibers together via, for example, heat, pressure, or sound (i.e., ultrasonic) energy.
In some processes a pair of heated calendering rolls can be used to create these fiber-to-fiber bonds. Typically, one of the calendering rolls comprises a plurality of protrusions which extend outward from its outer surface. A constant force is generally applied to one of the calendering rolls such that as the nonwoven web passes between the calendering rolls, the protrusions apply pressure to the nonwoven web. In general, at the location of applied pressure, at least one fiber-to-fiber bond is created.
In general, nonwoven webs which are to be used as receiving components are not completely bonded, e.g. 100% fiber-to-fiber bonds. Because the fiber-to-fiber bonds typically render the bonded areas unengageable by an engaging component, bonding the nonwoven web completely can yield a poorly performing receiving component. Therefore, the protrusions extending outward from the outer surface of the calendering roll are typically spaced apart such that a particular bonding pattern is created in the nonwoven.
Additionally, it may be desirable to have large, open, unbonded areas to assure that wherever a hook from the engaging component is placed an unbonded fiber or an unbonded portion of a bonded fiber is available to engage the hook. However, a bond pattern creating large, open, unbonded areas can have reduced strength in a cross machine direction because of the reduced number of fiber-to-fiber bonds in the unbonded areas. To compensate, some bond patterns can create fully enclosed areas e.g. fully bonded fibers surrounding unbonded fibers. However, a bond pattern which creates fully bonded fibers surrounding unbonded fibers can reduce the likelihood that a hook from an engaging component will find an unbonded fiber with which it can engage.
Additionally, the bond pattern can negatively impact the quality of the fiber-to-fiber bonds. For, example because conventional bond patterns do not completely bond the nonwoven web, the pressure applied to the nonwoven web as the nonwoven web passes through the calendering rolls can fluctuate. In some cases, the pressure fluctuations can cause higher pressures at some fiber-to-fiber bond sites and cause lower pressures at other fiber-to-fiber bond sites. The higher pressure can result in overbonding or even cutting through fibers (which weakens the resulting web). The lower pressure may result in a reduced percentage of bonded area being formed compared to the desired percentage of bonded area, lower bond strength and/or lower bond quality. Additionally, the lower pressure may cause reduced strength in the cross machine direction.
Consequently, there is a need to provide a fastening system which includes a receiving component having a bond pattern which reduces the pressure fluctuations experienced by the receiving component during processing while maintaining sufficient areas of unbonded fibers and/or unbonded portions of bonded fibers.